Distribution of music and video via a network such as the Internet is considered today as a highly-desired service. However, such a service may be subject to piracy and therefore efficient digital rights management (DRM) schemes are necessary to protect owner rights of content.
Conventional DRM schemes have drawbacks in that they affect privacy and anonymity of users. For example, some conventional DRM schemes require identification of a rendering device or binding of content to the rendering device which may reveal, indirectly, identity of an owner of the rendering device with which the content is associated. Furthermore, user actions required by some conventional DRM schemes, particularly when such user actions are associated with the content, may reveal private information, such as that a particular user uses specific content, identity of a user using the content, time periods when the user uses the content, and content preferences of the user.
Some aspects of technologies and related material that may be useful in understanding the present invention are described in the following publications:    published PCT Patent Application WO 02/079955 of NDS Limited, and corresponding U.S. patent application Ser. No. 10/472,286 of Shen-Orr et al, which describe a system and a method for providing variable security mechanisms for securing digital content;    a publication entitled “Google Video and Privacy”, by Ed Felten, dated 20 Jan. 2006, at www.freedom-to-tinker.com/?p=956;    an article entitled “How to share a secret”, by Adi Shamir in Communications of the ACM, 22(1), pages 612-613, 1979, available at www.cs.tau.ac.il/˜bchor/Shamir.html;    European Patent EP 0325238, which describes improved variants of the Fiat-Shamir identification and signature scheme;    U.S. Pat. No. 6,891,953 to DeMello et al, which describes a server architecture for a digital rights management system that distributes and protects rights in content;    Published US Patent Application 20050097558 of de Bonet, which describes systems and methods for architectures for a compact and efficient multimedia player; and    Published US Patent Application 20050135613 of Brandenburg et al, which describes a device and method for generating encrypted data, for decrypting encrypted data and for generating re-signed data.
The disclosures of all references mentioned above and throughout the specification, as well as the disclosures of all references mentioned in those references, are hereby incorporated herein by reference.